The traditional methods of screening for nearsighted and farsighted vision defects typically involve a series of tests on an individuals utilizing instrumentation, eye test charts, etc., to determine the individual's ability to establish visual acuity of objects at near or far distances. To applicant's knowledge specially selected colored test images have not been used to screen for nearsighted and farsighted vision defects.
Although the prior art teaches that red and green filters have been used for endpoint spherical refraction and for screening persons with color vision problems, the prior art does not teach method or apparatus for screening persons for nearsightedness or farsightedness using color as an indication of the type of visual problem of an individual.
The following group of prior art patents are related to the present invention in regards to apparatus for detecting color vision problems and in the general field of optometer technology.
______________________________________ U.S. Pat. No. Inventor Date of Issue ______________________________________ 2,023,246 V. M. SEARS DEC. 03, 1935 2,453,335 R. B. MORRIS NOV. 09, 1948 3,067,647 KICHIRO SATO DEC. 11, 1962 3,382,025 H. A. KNOLL MAY 07, 1968 3,870,376 H. L. LEDI JULY 20, 1976 4,408,846 R. F. BALLIET OCT. 11, 1983 5,067,806 A. KWASMAN NOV. 26, 1991 ______________________________________
From this group of patents the following relate to apparatus and method for screening for color vision problems, namely U.S. Pat. Nos. 2,453,335, 3,382,025, 3,970,376 and 5,067,806. The '355 Patent to Morris and the '025 Patent to Knoll teach anomaloscope devices for testing the color vision of a subject. The structures are configured to manipulate colored light in different patterns and intensity to determine a subject's ability to distinguish between different colors produced by the structure. The '376 Patent to Ledi teaches a device for testing the color vision of a subject using a plurality of pairs of test panels of different colors. The test method associated with the '376 device facilitates distinguishing a subject's deviations from normal color perception. The '806 Patent to Kwasman teaches a device for quick screening a subject's scotopic sensitivity using colored filter and test patterns.
The prior art patents directed at optometers for use in testing for nearsightedness and farsightedness are: U.S. Pat. Nos. 2,023,246, 3,067,647, and 4,408,846. The '246 Patent to Sears teaches a bi-prism device for testing a patients eyes wherein red and green filters are used to produce different focal points. The '647 Patent to Sato teaches an optometer device, while the '846 Patent teaches a method of improving visual acuity by performing a series of predetermined steps.
In the absence of prior art teachings, the applicant has determined that an individual is nearsighted if visual acuity is better on a test pattern colored by using a red filter over the light projecting the test image, i.e. a myopic screening test image, and that an individual is farsighted if visual acuity is better on a test pattern colored by using a green filter over the light projecting the test image, i.e. a hyperopic screening test image. Further, the applicant has determined that an individual has the best corrected vision if the visual acuity is good for both red and green colored test patterns viewed by the individual. The foregoing results, while determined in a clinical environment using eye charts embodying the myopic and hyperopic test patterns, the equivalent patterns are applicable in a non-clinical environment for screening for myopia or hyperopia on an individual, or group basis.
The myopic and hyperopic test patterns of the present invention are not limited to red and green colors, but are preferred because of their relationship to the color yellow which is the color best focused on the retina. Red and green colors essentially straddle yellow in terms of wavelength of their respective emitted light ray, red having a greater wavelength than green. This relationship results in red being best focused by an individual with a myopic condition and green being best focused by an individual with a hyperopic condition.
Thus, a need is seen to exist for a vision screening apparatus configured to provide a myopic screening test image in combination with a hyperopic screening test image for use as a visual-aid in a vision screening method for detecting myopia, or hyperopia defects on an individual, or group basis.